1. Technical Field of the Invention
The present invention relates to an upper tool holding apparatus in a press brake and an upper tool separating method from the upper tool holding apparatus, and more specifically, relates to an upper tool holding apparatus in which the installation, removal, and replacement of an upper tool can easily be performed to an upper table in the press brake, and an upper tool separating method from the upper tool holding apparatus.
2. Description of the Related Art
Conventionally, a press brake is arranged such that an upper table (another name is an upper ram) and a lower table (another name is a lower ram) are provided vertically opposite to each other, and is arranged such that properly either of the upper table or the lower table is vertically driven as a ram.
In a press brake with the above arrangement, a lower tool (die) is provided above the lower table in order to perform the bending work of a plate-like workpiece, and under the upper table, an upper tool (punch) is provided.
In the above arrangement, after positioning the workpiece on the lower tool, the bending work of the workpiece can be performed by engaging the upper tool and the lower tool.
By the way, in the press brake, it is arranged that in order to replace the upper tool, for example, because of the difference in the bending shape of the workpiece or the like, a lot of upper tool holding apparatus are attached under the upper table, and the upper tool is supported at the upper table by a lot of these upper tool holding apparatus in such a way that installation, removal, and replacement are possible.
A conventional upper tool holding apparatus is arranged such that the upper tool clamp is attached in a swingable way through a fastening bolt to the holder main body mounted under the upper table, and the upper portion of the upper tool inserted between this upper tool clamp and the holder main body is intensely tightened and fastened with the upper tool clamp by tightening the fastening bolt.
Accordingly, in the conventional arrangement, in order that the installation, removal, and replacement of the upper tool are performed to the upper table, it is required to handle a lot of fastening bolts provided to a lot of upper tool holding apparatus, and there was such a problem that this handling was extremely troublesome and difficult.
Furthermore, in the conventional upper tool holding apparatus, it is required that when the upper tool is mounted, the upper tool clamp is lightly fastened so that the upper tool may not fall, and after that, the upper tool clamp is intensely fastened in the state where the upper tool and the lower tool have been adjusted and centered, and there was such a problem that the handling is troublesome.
By the way, as a preceding example relating to the present invention, for example, there is Japanese Patent Application Laid-Open No. Hei 8-57542. In this preceding example, it is arranged that the upper tool is clamped by an upper tool clamp pivotally attached to the upper table of the press brake in a freely swingable way, between that and the holder main body. However, for example, in the case where a plurality of upper tools are installed to or removed from the holder main body in order to efficiently perform a plurality of bending steps of one product, it is necessary that the plurality of upper tools are simultaneously installed to or removed from the holder main body.
However, in the case where it is wanted to replace only 1 piece of upper tool among the plurality of upper tools, it is required to install or remove all tools again, and furthermore, in the case where a plurality of upper tools are installed to or removed from the surface side (front side) and the back side (rear side) of the holder main body, it is also impossible to perform the installation or removal simultaneously to the surface side and the back side, and therefore, there was such a problem that the efficiency in the replacement of the upper tool was low.